The tsetse fly (Glossina morsitans), vector of human and animal trypanosomiasis in Africa, has a reproductive strategy quite uncommon among insects. Offspring of this fly are retained within the body of the female throughtout larval development. This strategy requires a regulatory mechanism to coordinate egg maturation, larval development, mild synthesis, ovulation and parturition. The mother-larval interaction is being examined at the time of parturition to determine who (mother and larva) initiates the signal for parturition. Preliminary evidence suggests a role for cyclic AMP as a mediator of ovulation and parturition. Topical applications of juvenile hormone induce tsetse females to abort their larvae. Abortions can be most readily induced with juvenile hormone during the first half of the pregnancy cycle. Application later in the cycle fails to elicit abortion but disrupts embryogenesis in the subsequent pregnancy cycle.